Steam generating unit



Nov. 17, 1964 M. H. Kul-:NER 3,157,163

STEAM GENERATING UNIT Filed Oct. 19, 1961 INVENTOR lax H. Kahne-rcombustion chamber.

United States Patent Oilice 3,l57,lb3 Patented Nov. 17, 1964 3,157,163STEAM GENERATDJG UNT Max H. Kuhner, alrham, Mass., assigner to RileyStoner Corporation, Worcester, Mass., a corporation of MassachusettsFiled Get. 19, 1961, Ser. No. 146,123 4- Claims. (Cl. inw-235) Thisinvention relates to a steam generating apparatus and more particularlyto apparatus arranged to produce steam for the generation of electricalpower or the like.

in the design of steam generating units and, particularly, of those inan intermediate range from, say, 75,90() to 260,060 lbs. per hour, oneof the drawbacks encountered is that these units are quite expensivebecause each unit requires an individual custom design. Furthermore, inorder to obtain complete combustion of the fuel before the products ofcombustion pass over the convection surfaces, it has been necessary toprovide an extremely large ln addition, extremely large buildings havebeen required to maintain such boilers; in many cases the fact that vthe burners are on diiterent levels means that access can be had to the.burners only by the operator climbing on catwalks or the like. Theseand other difficulties have been experienced by the prior art devicesand have been obviated in a novel manner by the present invention.

it is, therefore, an outstanding obiect of the invention to provide asteam generating unit of the intermediate range of sizes in which thelongitudinal design may remain the same for the entire range and thecapacity of the unit may be increased for a speciiic application merelyby making the furnace wider.

Another object of this invention is the provision of a compact steamgenerating unit which is inexpensive to manufacture for a given capacityand which requires a relatively small combustion chamber.

A further object oi the present invention is the provision of a steamgenerating unit for use in t e intermediate range of capacity in whichcombustion is completed well before the products of combustion pass intothe convection passes.

Another object of the invention is the provision of an intermediaterange steam generating unit in which the back passes and the maincombustion chamber are shaped to lit together geometrically to providean inexpensive, compact unit.

With these and other objects in view, as will be apparent to thoseskilled in the art, the invention resides in the combination ol partsset forth in the specification and covered by the claims appendedhereto.

The character of the invention, however, may be best understood byreference to one of its structural forms as illustrated by theaccompanying drawing in which:

The single ligure shows a longitudinal, vertical, sectional view of asteam generating unit embodying the principles of the present invention.

The steam generating unit, indicated generally by the reference numeral1), is shown mounted in association v with the operating floor 1l of abuilding in which the unit is housed. The unit consists generally of aboiler l?. and a furnace 13 which are inter-related in the usual manner.The furnace 13 consists generally of a front wall 15:-, a rear wall l5,side walls 16, a bottom wall 17, and a roof wall ld deilning avertically-elongated combustion chamber 19. The boiler 12 consists of anupper steam-andwater drum 2l and a lower mud drum 22 which is parallelwith and spaced from the drum 2l. A. number of downcomer tubes 23 extendfrom the drum 21 to the drum 22. 4on the rearward side of a verticalbaille 24 which extends vertically downwardly from the bottom of thedrum 21. Forwardly of the baille 2d a number of riser tubes 25 connectthe drum 22. to the drum 2l. A large downcomer tube 26 connects the muddrum 22 to a header 2'7 which underlies the rear portion of the bottomwall 17 and is parallel to and spaced downwardly from the drums 21 andZZ. A number of water-wall tubes 28 extend from the header 27 up theback rear wall 15 and enter the steamand-water drum 21. Other water-walltubes 29 extend from the header 27 along the bottom wall 17 up the frontwall le and over the undersurface of the roof wall 1S to enter thesteam-and-water drum 2i. Under each side wall 16 is located alongitudinal header 31 which is connected to the mud drum 22 by adowncomer 32. From each header 3l extend water-wall tubes 33 which liealong the surface of the side walls 16 and discharge into a headerlocated above the roof wall 18, which header is also connected to thesteam-and-water drum 21. A front wall 14 extends vertically upwardlyfrom the bottom wall 17 for a short distance and then merges into adownwardlyfacing, upwardly-and-inwardly inclined portion 35 which mergeswith an upper vertical portion 35. This portion extends upwardly untilit meets the roof wall 18. The rear wall l5 also extends verticallyupwardly the same short distance above the bottom wall 17 and is thenprovided with a downwardly-facing, upwardly-and-forwardly inclinedportion 37 which merges at its upper portion with an upper verticalportion 3?. The upper part of the rear wall l5 has the refractoryremoved and the water-wall tubes 2% are bent longitudinally to provide agas oil-take 39. The space between the vertical downwardly-dependingbaille Zd and the upwardly-extending rear wall l5 provides a convectionpass il which contains a convection superheater 4t2. @ne end of thissuperheater is attached to the top of the steam-and-water drum 21 andthe other end is connected to the superheated steam header 43 which liesabove the roof wall 18. A gas-reversal passage i4 lies between the lowerend of the baille 24S and the upper surface of the mud drum 22 andanother gas-reversal passage 45 underlies the rnud drum 22 and lieswithin an ash hopper lo whose forward wall is formed by the inclinedportion 37 of the rear wail 15 and is provided with another inclinedwall 47 located rearwardly of the mud drum. The upper edge of theinclined wall i7 ot the ash hopper merges with a vertical back wall lf3which defines with the baille 24 a back pass i9 in which most of thedowncomer tubes 23 reside. A series of battles 51 extend from thebailles 24 and the rear wall 4? to cause sinuous flow of gas over thebundle of downcomer tubes. Rearwardly of the steam-and-water drum 2l thegases llow up the back pass 49 over a damper S2 to a breaching 53 fordisposal. The bottom of the ash hopper i7 is provided with a verticalslot S3 leading downwardly to a horizontal longitudinal passage 5d fromwhich a number of nozzles lead through the bottom portion of the rearwall l5 into the combustion chamber 19. A motor-driven fan 5o dischargesair at high velocity into the passage dll and into the nozzles S5.Extending upwardly into the hopper and into the gas passage i5 is a duct57 having a damper 5S whose setting in the duct S7 is controlled by amanuallyoperated rod 59. Mounted on the inclined portion 35 of the frontwall i4 is a burner el which is of the inter-tube directional-flame typeshown and described in the patent of Craig No. 2,853,659 having acentral fuel gun 62 which receives fuel from a duct 63. The burner isprovided with a gas-electric ignition gun dd and is provided with ahousing e5 which receives air from a duct do connected at its other endto a forced draft fan 67 and provided with an air-ilow damper d. Theburner has upper vanes 6? mounted on horizontal axes and adjustable asto inclination to the horizontal by means of a control rod 71. Below thefuel gun 62 the burner is provided with lower vanes 72 also mounted foradjustment about horizontal axes by means of a control rod 73. The fuelgun o2 is shown ot the type having an outer pulverized-coal burner whichreceives its fuel from the fuel duct 63 and an inner gas gun 7d whichreceives its fuel from a gas pipe 75. it will be understood thatalthough only one burn-er 6l is shown on the inclined portion 35 of thefront wall, that any number of burners may be used and that theiroperating portions and areas are readily accessible from the operatingfloor 1l. The bottom wall 17 is provided with a slag opening 76 which islined with water cooling pipe 77. Under the opening 76 is hung a slagtank 7S having a pool 79 of water and `at its bottom a screw-type ashconveyor 8l. Water injection pipes $2 and are located at the upper partofthe tank 7S and are provided with nozzles for spraying a continuousstream of Water across the tank in the path of the downwardly-fallingmolten slag. The inclined portions 3S and 37 of the front wall i4 andrear Wall l5, respectively, define with the bottom wal i7 ahigh-temperature lower cell or combustion chamber S4, while the verticalportion 36 of the front wall ld and the vertical portion 3d of the rearwall l5 serve to define a narrow upper combustion chamber S5.

It will be understood that a plurality of burners E usually be providedtransversely of the furnace on clined surface 35' of the front wall;there also is a of the injection nozzles 55 along the lower porti ofrear wall l5. The slot 53 from the hopper the full Width of the furnace,as does the hopper itself and the recirculating gas duct 57 with itsdamper. A plurality of injection air fans 56 may also be used.

The operation of the apparatus will now be readily understood in view ofthe above description` 2l operates in the usual way with water leavingthe steamand-water drum through the downcomers to YElow into the muddrum 22;. The water flows from the mud drum through the downcomers 216and 32 into the headers 27 and 31. From that point the water risesthrough the water-wall tubes 2S, 29, and 33 and, eventually, the mixtureof steam and water flows into the steam-and-water drum 2l where thesteam moves to the top and the water circulates again. The steam passesthrough the superheater 42 into the superheated steam header 43 and iseventually used in a turbine or other steam equipment. The operation ofthe furnace is also in the usual manner; air from the forced-draft fan67 flows into the burner til and into the furnace over the vanes 69 and71?; whose angles have been set by use of the actuating handles and 73,respectively. Fuel enters the system through tl e duct 63 and thepulverized coal gun 62 as well as through the gas pipe 75 and the gasgun 74. The air and fuel mix in the combustion chamber and are ignitedand maintained in ignition by the ignition gun 64. rthe rapidly-burningfuel and air mixture is directed by the vanes 69 and "2 downwardlytoward the bottom wall T17 of the furnace. The burning mixture is thenreversed, moves under the inclined portion 3'7 of the rear wall (whichportion acts in the nature of a rear arch), and then moves verticallyupwardly into the upper combustion chamber S5. lt can be seen that theupper combustion chamber 35 is quite narrow compared to the lowercombustion chamber and, therefore, there is a tendency for the productsof combustion to linger in the lower combustion chamber which, becauseof the high rate of heat release, becomes very hot and forms ahigh-temperature cell. The exit from the high-temperature lowercombustion chamber Sd is, of course, the passage between the closestadjacent portions of the inclined portion 35 of the front wall and theinclined portion 37 of the rear wall. Heat transfer to the Water tubestakes place mainly by radiation in the entire combustion chamber i9. Theproducts of combustion pass from the combustion chamber rearwardlythrough the gas off-take 39 into the convection pass #il Where it comesinto heat transfer relationship to the superheater d?. and to the risertubes The gases pass downwardly through lthe convection pass il and passaround the mud drum Z2. Some of them pass above the mud drum in thepassage lil and some move down a 1 Will "ai i i r1.9 (ai dill throughthe hopper 45 in the passage In either case, they are reversed and moveupwardly through the back pass 49 in a sinuous flow brought about by thebafdes 5l. During the reversal in the passages 44 and 45 a considerableamount of the ash in the gases is thrown by centrifugal force into thehopper 46 where it slides down the outer surface of the inclined portion37 of the rear wall and the inner surface of the inclined wall 47, thesemaking up thc walls of the hopper. The ash passes downwardly through theslot 53 into the passage 54 where it meets the air blast from the fan 56and is thrown by the ejector principle into the nozzle 5S and into thehightemperature lower combustion chamber 84. The ilyash which is in thisway introduced into the furnace again contains a considerable amount ofunburned combustible which is now burned; the non-combustible is meltedinto slag by the high average temperature existing in thishightemperature cell. All of the slag formed in the hightemperature cellflows onto the inner surface of the bottom wall i7 and eventually owsthrough the slag opening 76 where it is cooled by the spray from thepipes SZ and and falls into the pool 79 in the slag tank 78. Eventually,it is removed from the bottom of the slag tank by the conveyor Si. it isadvantageous, of course, not only to burn out the combustible left inthe ash which accumulates in the hopper 46 but also this is a convenientway of disposing of the ash itself, since, as solidified slag, it isextremely concentrated in form, easy to transport and disposed of, andis saleable for use in the paving of roads and similar uses.

t may be desirable at times to regulate the temperature of steamreaching the superheated steam header 43. For this purpose, it ispossible to recirculate a portion of the products of combustion. By aproper setting of the damper 5S in the duct 57, the ejector action ofthe air from the fan 55 passing over the bottom of the duct 57 willcause products of combustion to be drawn from the back passes of thefurnace and to be thrown with the ash through the nozzle 55 into thehigh-temperature cell. The location of the upper end of the duct 57 isselected so that the gas drawn into the duct will be relatively free ofash; for instance, it might be located behind the mud drum 22. In anycase, small amounts of llyash returned to the furnace by the gasrecirculation duct are not harmful and will be disposed of in the samemanner as the rest of the ash from the hopper d6. The recirculated gas,however, ilows from the nozzle 55 up along the inclined portion 37 ofthe rear wall l5. From there it moves up along the rear wall 15, beingforced into that position by the tlame from the burner di. The gasrecirculated in this manner serves two purposes. First of all, itincreases the mass llow of gas which flows out of the gas olf-take 39and down the convection pass 41 over the superheater 42, thus increasingthe temperature of gas which flows from the superheater into thesuperheated steam header 43. The gas thus recirculated is also coolerthan the gas from the flame and serves as an inert cooling blanket alongthe back wall, so that the flame from the burner 61 as it reversesitself and moves upwardly along the inclined surface 37 and the uppervertical portion 38 of the rear wall is maintained some distance awayfrom the rear wall by the blanket of recirculated gas. This prevents thewater-wall tubes and refractory from becoming too hot and also preventsthe formation of slag deposits on these walls, tending to keep the wallsclean and free of slag.

Manipulation of the control rods 71 and 73 permits changing the anglesof the varies 69 and 72 not only relative to their horizontal positionsbut also relative to one another, so that complete control of the flamein the hightemperature lower combustion chamber is permitted. Since thehigh-temperature cell brings about very complete combustion of the fuel,the gases which enter the upper combustion chamber tend to be inert andthe temperature gradient from side 16 to side 16 of the unit is quiteeven. It is necessary, therefore, to provide only a small uppercombustion chamber 85 since room for combustion is not necessary.Furthermore, this present construction provides for small distance fromthe front wall 14 to the rear wall 15 in the upper combustion chamber asis evident in the drawings. This permits a higher rate of transfer fromthe fuel to the water-wall tubes, since radiant transfer from a givenparticle is inversely proportional to the square of the distance fromthe particle to the surface in question. The need for a large combustionchamber is thus obviated, resulting in a much less expensive steamgenerating unit. At the same time, the fact that the inclined portion 37of the rear wall not only serves as part of the high-temperature lowercombustion charnber 84 but also as the bottom of the hopper 46 providesa geometric inter-relationship of the parts which provides a compactsteam generating unit, thus requiring `a relatively small supportingstructure and building for the housing of the unit.

It is obvious that minor changes may be made in the form andconstruction of the invention without departing from the material spiritthereof. It is not, however, desired to confine the invention to theexact form herein shown and described, but it is desired to include allsuch as properly come within the scope claimed.

The invention having been thus described, What is claimed as new anddesired to secure by Letters Patent, is:

1. A steam generating unit, comprising a boiler having a steam-and-waterdrum, a furnace having front, rear, side, roof, and bottom wallsdefining a combustion chamber, a header parallel to the said drumunderlying the floor wall of the chamber, water-wall tubes extendingfrom the header over the oor wall, over the front wall, and along theroof wall to the steam-and-water drum, water- Wall tubes extending fromthe header over the rear Wall to the drum, the front wall having adownwardly-facing inclined portion adjacent the floor Wall, the rearwall having a downwardly-facing inclined portion adjacent the ffoorwall, a rear housing Wall defining with the said rear wall a back passenclosing the said heat exchanger, the lower part of the said rearhousing wall being inclined to the Vertical and lying in opposition tothe said inclined portion forming a V-shaped ash hopper which underliesthe drum, the said inclined portions serving to define ahigh-temperature lower combustion chamber with the fioor wall, theinclined portions of the front and rear walls extending toward oneanother, these Walls having vertical portions extending upwardly fromthe upper parts of the inclined portions to provide a relatively narrowupper combustion chamber, a gas off-take through the rear Wall adjacentthe roof wall, a convection heat exchanger section connected to andunderlying the said drum, the said section lying adjacent the verticalportion of the rear Wall and lying over the said inclined portion, andat least one burner mounted on the said inclined surface of the frontwall.

2. A steam generating unit, comprising a boiler having a steam-and-waterdrum, a furnace having front, rear, side, roof, and bottom wallsdefining a combustion chamber, a header parallel to the said drumunderlying the floor Wall of the chamber, water-wall tubes extendingfrom the header over the floor wall, over the front Wall, and along theroof wall to the steam-and-water drum, Waterwall tubes extending fromthe header over the rear Wall to the drum, the front Wall having adownwardly-facing inclined portion adjacent the fioor wall, the rearwall having a downwardly-facing inclined portion adjacent the floorwall, a rear housing Wall defining with the said rear wall a back passenclosing the said heat exchanger, the lower part of the said rearhousing Wall being inclined to the vertical and lying in opposition tothe said inclined portion forming a V-shaped ash hopper which underliesthe drum, the said inclined portions serving to define ahigh-temperature lower combustion chamber with the floor Wall, theinclined portions of the front and rear walls extending toward oneanother, these walls having vertical portions extending upwardly fromthe upper parts of the inclined portions to provide a relatively narrowupper combustion chamber, a gas off-take through the rear wall adjacentthe roofwall, a convection heat exchanger section connected to andunderlying the said drum, the said section including a superheater lyingadjacent the vertical portion of the rear wall and lying over the saidinclined portion and receiving downwardly-flowing gas from the saidoff-take, and at least one burner mounted on the said inclined surfaceof the front wall.

3. A steam generating unit, comprising a boiler having a steam-and-waterdrum, a furnace having front, rear, side, roof, and bottom Wallsdefining a combustion chamber, a header parallel to the said drumunderlying the fioor wall of the chamber, water-Wall tubes extendingfrom the header over the floor wall, over the front Wall, and along theroof wall to the steam-and-Water drum, water- Wall tubes extending fromthe header over the rear wall to the drum, the front wall having adownwardly-facing inclined portion adjacent the iioor wall, the rearwall having a downwardly-facing inclined portion adjacent the floorwall, a rear housing Wall defining with the said rear wall a back passenclosing the said heat exchanger, the lower part of the said rearhousing wall being inclined to the vertical and lying in opposition tothe said inclined portion forming a V-shaped ash hopper which underliesthe drum, the said inclined portions serving to define ahigh-temperature lower combustion chamber with the floor wall, theinclined portions of the front and rear walls extending toward oneanother, these walls having vertical portions extending upwardly fromthe upper parts of the inclined portions to provide a relatively narrowupper combustion chamber, a gas off-take through the rear wall adjacentthe roof Wall, a convection heat exchanger section connected to andunderlying the said drum, the said section lying adjacent the verticalportion of the rear wall and lying over the said inclined portion, andat least one burner mounted on the said inclined surface of the frontwall, the burner including a fuel gun and air-directing varies mountedfor pivotal adjustment about horizontal axes, there being no burners onthe inclined surface of the rear wall.

4. A steam generating unit, comprising a boiler having a steam-and-waterdrum, a furnace having front, rear, side, roof, and bottom walls deninga combustion chamber, a mud drum underlying and spaced from thesteamand-Water drum, downcomer tubes connecting the two drums, atransverse header underlying the floor wall of the chamber, water-walltubes extending from the header over the door wall, over the front wall,and along the roof wall to the steam-and-water drum, water-wall tubesextending from the header over the rear wall to the mud drum, the frontWall having a downwardly-facing inclined portion adjacent the floorWall, the rear Wall having a downwardly-facing inclined portion adjacentthe floor wall, a rear housing wall defining with the said rear wall aback pass enclosing the said heat exchanger, the lower part of the saidrear housing wall being inclined to the vertical and lying in oppositionto the said inclined portion of the rear wall, the said lower part andthe said inclined portion forming a V-shaped ash hopper which underliesthe drum, the said inclined portions serving to define ahigh-temperature cell with the fioor wall, and a directional dame burnermounted on the said surface of the front Wall.

References Cited in the file of this patent UNITED STATES PATENTS1,970,109 Stratton Aug. 14, 1934 2,336,236 Foresman et al Dec. 7, 19432,853,059 Craig Sept. 23, 1958 2,905,155 Grossman Sept. 22,1959

FCREIGN PATENTS 759,462 Great Britain Oct. 17, 1956

1. A STEAM GENERATING UNIT, COMPRISING A BOILER HAVING A STEAM-AND-WATERDRUM, A FURNACE HAVING FRONT, REAR, SIDE, ROOF, AND BOTTOM WALLSDEFINING A COMBUSTION CHAMBER, A HEADER PARALLEL TO THE SAID DRUMUNDERLYING THE FLOOR WALL OF THE CHAMBER, WATER-WALL TUBES EXTENDINGFROM THE HEADER OVER THE FLOOR WALL, OVER THE FRONT WALL, AND ALONG THEROOF WALL TO THE STEAM-AND-WATER DRUM, WATERWALL TUBES EXTENDING FROMTHE HEADER OVER THE REAR WALL TO THE DRUM, THE FRONT WALL HAVING ADOWNWARDLY-FACING INCLINED PORTION ADJACENT THE FLOOR WALL, THE REARWALL HAVING A DOWNWARDLY-FACING INCLINED PORTION ADJACENT THE FLOORWALL, A REAR HOUSING WALL DEFINING WITH THE SAID REAR WALL A BACK PASSENCLOSING THE SAID HEAT EXCHANGER, THE LOWER PART OF THE SAID REARHOUSING WALL BEING INCLINED TO THE VERTICAL AND LYING IN OPPOSITION TOTHE SAID INCLINED PORTION FORMING A V-SHAPED ASH HOPPER WHICH UNDERLIESTHE DRUM, THE SAID INCLINED PORTIONS SERVING TO DEFINE AHIGH-TEMPERATURE LOWER COMBUSTION CHAMBER WITH THE FLOOR WALL, THEINCLINED PORTIONS OF THE FRONT AND REAR WALLS EXTENDING TOWARD ONEANOTHER, THESE WALLS HAVING VERTICAL PORTIONS EXTENDING UPWARDLY FROMTHE UPPER PARTS OF THE INCLINED PORTIONS TO PROVIDE A RELATIVELY NARROWUPPER COMBUSTION CHAMBER, A GAS OFF-TAKE THROUGH THE REAR WALL ADJACENTTHE ROOF WALL, A CONVECTION HEAT EXCHANGER SECTION CONNECTED TO ANDUNDERLYING THE SAID DRUM, THE SAID SECTION LYING ADJACENT THE VERTICALPORTION OF THE REAR WALL AND LYING OVER THE SAID INCLINED PORTION, ANDAT LEAST ONE BURNER MOUNTED ON THE SAID INCLINED SURFACE OF THE FRONTWALL.